3. Managed Interfaces

OpenJPA's managed interface feature allows you to define your object model
entirely in terms of interfaces, instead of concrete classes. To use this
feature, you must annotate your managed interfaces with the
ManagedInterface annotation, and use the
OpenJPAEntityManager.createInstance(Class) method to
create new records. Note that createInstance() returns
unmanaged instances; you must pass them to
EntityManager.persist() to store them in the database.